From patchwork Sun Jun 9 06:41:18 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tetsuo Handa X-Patchwork-Id: 10983547 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D26551398 for ; Sun, 9 Jun 2019 06:43:35 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BCB7A28AB8 for ; Sun, 9 Jun 2019 06:43:35 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id ADB7028B0B; Sun, 9 Jun 2019 06:43:35 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 392BC28AB8 for ; Sun, 9 Jun 2019 06:43:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726552AbfFIGmm (ORCPT ); Sun, 9 Jun 2019 02:42:42 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:62795 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726178AbfFIGmm (ORCPT ); Sun, 9 Jun 2019 02:42:42 -0400 Received: from fsav107.sakura.ne.jp (fsav107.sakura.ne.jp [27.133.134.234]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id x596fQHD002128; Sun, 9 Jun 2019 15:41:26 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav107.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav107.sakura.ne.jp); Sun, 09 Jun 2019 15:41:26 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav107.sakura.ne.jp) Received: from [192.168.1.8] (softbank126012062002.bbtec.net [126.12.62.2]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id x596fI6M002079 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Sun, 9 Jun 2019 15:41:26 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Subject: [PATCH] tomoyo: Don't check open/getattr permission on sockets. To: Al Viro , linux-fsdevel@vger.kernel.org Cc: syzbot , jmorris@namei.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, serge@hallyn.com, syzkaller-bugs@googlegroups.com, takedakn@nttdata.co.jp References: <0000000000004f43fa058a97f4d3@google.com> <201906060520.x565Kd8j017983@www262.sakura.ne.jp> From: Tetsuo Handa Message-ID: <1b5722cc-adbc-035d-5ca1-9aa56e70d312@I-love.SAKURA.ne.jp> Date: Sun, 9 Jun 2019 15:41:18 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <201906060520.x565Kd8j017983@www262.sakura.ne.jp> Content-Language: en-US Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP syzbot is reporting that use of SOCKET_I()->sk from open() can result in use after free problem [1], for socket's inode is still reachable via /proc/pid/fd/n despite destruction of SOCKET_I()->sk already completed. But there is no point with calling security_file_open() on sockets because open("/proc/pid/fd/n", !O_PATH) on sockets fails with -ENXIO. There is some point with calling security_inode_getattr() on sockets because stat("/proc/pid/fd/n") and fstat(open("/proc/pid/fd/n", O_PATH)) are valid. If we want to access "struct sock"->sk_{family,type,protocol} fields, we will need to use security_socket_post_create() hook and security_inode_free() hook in order to remember these fields because security_sk_free() hook is called before the inode is destructed. But since information which can be protected by checking security_inode_getattr() on sockets is trivial, let's not be bothered by "struct inode"->i_security management. There is point with calling security_file_ioctl() on sockets. Since ioctl(open("/proc/pid/fd/n", O_PATH)) is invalid, security_file_ioctl() on sockets should remain safe. [1] https://syzkaller.appspot.com/bug?id=73d590010454403d55164cca23bd0565b1eb3b74 Signed-off-by: Tetsuo Handa Reported-by: syzbot --- security/tomoyo/tomoyo.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c index 716c92e..9661b86 100644 --- a/security/tomoyo/tomoyo.c +++ b/security/tomoyo/tomoyo.c @@ -126,6 +126,9 @@ static int tomoyo_bprm_check_security(struct linux_binprm *bprm) */ static int tomoyo_inode_getattr(const struct path *path) { + /* It is not safe to call tomoyo_get_socket_name(). */ + if (path->dentry->d_inode && S_ISSOCK(path->dentry->d_inode->i_mode)) + return 0; return tomoyo_path_perm(TOMOYO_TYPE_GETATTR, path, NULL); } @@ -316,6 +319,10 @@ static int tomoyo_file_open(struct file *f) /* Don't check read permission here if called from do_execve(). */ if (current->in_execve) return 0; + /* Sockets can't be opened by open(). */ + if (f->f_path.dentry->d_inode && + S_ISSOCK(f->f_path.dentry->d_inode->i_mode)) + return 0; return tomoyo_check_open_permission(tomoyo_domain(), &f->f_path, f->f_flags); }